Human disease data is a cornerstone of biomedical research for identifying drug targets, connecting genetic variations to phenotypes, understanding molecular pathways relevant to novel treatments and coupling clinical care and biomedical research. Consequently, there is a significant need for a standardized representation of human disease to connect disease concepts across resources, to support development of computational tools that will enable robust data analysis and integration and to continually incorporate new insights regarding our understanding of disease pathogenesis. For the past 13 years, the Disease Ontology team has been focusing on developing and applying an etiology based Human Disease Ontology (DO) and providing the biomedical community with a knowledgebase of integrated rare and common disease terms to support disease annotations for genomes, genes, genetic variants, associated biomedical data and literature. Conservatively, based on available resource statistics, terms from the DO have been annotated to over 150,000 biomedical data elements and citations. We have developed the DO, representing 6,782 human diseases and the DO web interface (http://www.disease-ontology.org) and RESTful API to enable semantic exploration of disease etiology and aligned disease concepts representing 36,711 clinical vocabulary cross- references. The 10-fold increase of the number of published clinical and experimental studies per year (PubMed: Clinical Study) in the past four decades, with 43,401 PubMed articles in 2014 compared to 3,269 in 1975, has markedly expanded our understanding of disease mechanisms. We have identified two main areas of improvement in the DO (1.0) necessary to represent this growing body of knowledge: (1) representing cellular, molecular and environmental mechanisms of disease as distinct disease profiles within the DO and (2) representing alternative classifications of complex disease in order to address clinical use cases for complex diseases. We thus propose to develop the DO (2.0), an integrative disease mechanism framework for disease characterization and annotation, with the goal to represent distinct disease profiles and improve upon the existing single profile (DO 1.0) or mixed profile classifications (ORDO, NCIthesaurus, MonDO). We believe DO (2.0) will provide both genomic and clinical research communities with a versatile system that will enable researchers to perform more accurate and comprehensive analysis of common cellular, molecular or environmental disease mechanisms. Utilization of the DO will be promoted in the clinical and biomedical communities through high profile publications, conferences and workshops.